This invention relates to a process for making an isoflavone concentrate product from soybeans. Isoflavones are a unique class of phytoestrogens--plant hormones--that naturally occur in soybeans.
It is anticipated that consumer demand for soy isoflavones will continue to grow. Scientists have demonstrated that isoflavones have the ability to inhibit cancer cell growth, and some researchers believe that isoflavones may contribute to soy's ability to lower blood-cholesterol levels.
Research shows that soy isoflavones have a wide range of health benefits that include moderating normal symptoms associated with menopause and promoting bone and heart health. It appears that about 100 milligrams of isoflavones (expressed in the glucoside form) are necessary to deliver most of these health benefits. This is about the average amount consumed daily by Asian men and women who have a much lower incidence of heart disease, osteoporosis and uncomfortable menopausal symptoms compared to Western societies.
Some women's health problems during and after middle age are related to a changing hormonal state. Consuming soy isoflavones can help moderate the natural hormonal changes associated with several menopausal and postmenopausal symptoms.
Soy isoflavones are potent antioxidants capable of reducing the amount of LDL-cholesterol (bad cholesterol) that undergoes modification in the body. Entry of the modified LDL-cholesterol into the walls of blood vessels contributes to the formation of plaques. These plaques cause the blood vessels to lose their ability to function normally. Research in both animals and humans shows that ingesting soy isoflavones can help maintain normal blood vessel function.
Soy isoflavones are actively studied for their effects on maintaining and improving bone health. Women can lose up to 15% of their total bone mass in the early years following the onset of menopause. This loss can be quite detrimental, particularly to women who enter menopause with weaker bones. Emerging research shows that isoflavones appear to play a role in both preventing bone loss and increasing bone density.
The principal types of isoflavones found in soybeans are glucones (with sugars) and aglucones (without sugars). Glucones have the glucose molecule attached, and include genistin, daidzin and glycitin. Aglucones are isoflavones without the glucose molecule, and they include genistein, daidzein and glycitein. It is an object of this invention to produce products with the isoflavones genistein, daidzein and glycitein in similar proportions as those found naturally in soybeans when isoflavones are reported in the aglucone form.
The prior art teaches isolating genistin from hexane-extracted soybean flakes. Walter ("Genistin (an Isoflavone Glucoside) and Its Aglucone, Genistein, from Soybeans," J. of Am. Chem. Soc., 63, 3273 (1941)) describes a method involving, among other steps, extracting the flakes with methanol, precipitating with acetone and recrystallizing with ethanol.
U.S. Pat. No. 5,141,746 (Fleury et al.) describes a method for preparing an impure extract of two specific isoflavones daidzin malonate and genistin malonate. Fleury describes a method involving, among other steps, mixing hexane-defatted ground soybeans with 80 percent (%) aqueous methanol, filtering and drying; adjusting pH multiple times with, among other chemicals, hydrochloric acid and sodium hydroxide, and extracting with an organic solvent, such as butanol.
U.S. Pat. No. 5,352,384 (Shen) describes making an aglucone enriched fiber. Shen describes solubilizing isoflavones from soy flour by, among other steps, forming a slurry with an extractant, such as sodium. poasum or calcium hydroxide, to adjust the pH to te proteins' isoelectric point of 6.7-9.7, and reacting the slurry with the enzyme .beta.-glucosidase.
The use of multiple acids/bases and organic solvents to extract isoflavones from soybeans makes it costly to commercially manufacture soy isoflavone products. The use of a number of materials to extract isoflavones increases raw material, equipment and labor costs.
It is apparent that an efficient process for removing isoflavones from soybeans is needed. It also is apparent that a low-cost soy isoflavone concentrate (SIC) product is needed.
The invention does not use other chemicals, such as, acetone, hydrochloric acid or sodium hydroxide, to manufacture the SIC product from soy solubles. Soy solubles are recovered from alcohol-extracted hexane-defatted soybean flakes. These solubles, sometimes called soy "molasses", are desolventized, such that they contain less than 0.5% alcohol, and typically are evaporated to 60% solids.
It was discovered that soy solubles, on average, contain 3.31 milligrams per gram (mg/g) genistin on a wet basis and have a total isoflavone content (i.e., daidzin, glycitin, genistin, mal-daidzin, mal-genistin, daidzein, glycitein, genistein and some unidentified isoflavones) of 8.96 mg/g on a wet basis as determined by high performance liquid chromatography (HPLC). The genistin to daidzin ratio of soybeans is about 1 to 1 and that ratio in soy solubles was found to be about 1-1.5 to 1.
It was further discovered that if the soy solubles are diluted with water to form a slurry and the undissolved solids are removed from the slurry to form a wet "cake", the cake contains a significantly concentrated amount of isoflavones.
It was further discovered that if the soy solubles, which have about 20 mg/g isoflavones on a dry basis, are diluted with water to a certain percent solids and the undissolved solids are separated from the diluted solubles with a certain type of centrifuge that the isoflavone content of the solubles can be concentrated by at least 2 times. It was surprising and unexpected to learn that a product with such a high isoflavone content could be produced from the soy solubles without adjusting the solubles' pH with bases or extracting the solubles with another solvent.